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This composite image shows suspected plumes of water vapor erupting at the 7 o’clock position off the limb of Jupiter’s moon Europa. The plumes were photographed by the Hubble Space Telescope Imaging Spectrograph and were seen in silhouette as the moon passed in front of Jupiter. Hubble’s ultraviolet sensitivity allowed for the suspected plumes, which rise at least 160 kilometers above Europa’s icy surface, to be observed. The Hubble STIS data was obtained on Jan. 26, 2014. The image of Europa is superimposed on the Hubble STIS data and was assembled from data gathered during the Galileo and Voyager missions. Image courtesy NASA, European Space Agency, Space Telescope Science Institute/W. Sparks, U.S. Geological Survey Astrogeology Science Center.

NASA announced Monday that scientists using the Hubble Space Telescope have found evidence of water plumes on Europa, which means that spacecraft may be able to explore the moon’s ocean without the need to penetrate its icy surface.

A research team led by astronomer William Sparks of the Space Telescope Science Institute in Baltimore used a technique that has often been instrumental in discovering exoplanets to identify the plumes.

As an exoplanet moves in front of its star, the light from that star changes as it passes through the exoplanet’s atmosphere. This happens because the light encounters a variety of molecules.

On Europa, Sparks and his team noticed that the molecules in the moon’s atmosphere included water vapor. That led them to embark on a quest to determine whether water from Europa’s subsurface ocean is being expelled into space.

The scientists observed Europa pass in front of Jupiter, from which the Sun’s light would be reflected through the atmosphere of the Jovian moon, ten times in 15 months. On three of the occasions water vapor was detected.

“This is an exciting find because it potentially gives us access to the ocean below,” Sparks said at a NASA teleconference on Monday.

Scientists are interested in sampling Europa’s ocean because it may provide indications of whether the moon is, or ever has been, hospitable to life.

“On Earth, life is found wherever there is energy, water, and nutrients, so we have a special interest in any place that has those characteristics,” Dr. Paul Hertz, director of NASA’s astrophysics division in Washington, D.C., said. “Europa might be such a place.”

Europa has a large sub-surface ocean that is thought to contain more water than all of the oceans on Earth. However, the satellite also has a thick icy crust atop that ocean.

The water plumes may rise as high as 200 kilometers off Europa’s surface.

“Europa’s ocean is considered to be one of the most promising places that could potentially harbor life in the solar system,” Geoff Yoder, the acting associate administrator for NASA’s Science Mission Directorate, said. “These plumes, if they do indeed exist, may provide another way to sample Europa’s subsurface.”

A team led by Lorenz Roth of the Southwest Research Institute in Austin, Tex. identified water plumes rising from Europa’s south pole once during 2012.

The Roth group used the Hubble Space Telescope’s Imaging Spectrograph to identify hydrogen and oxygen ions by the ultraviolet radiation they emit after particles accelerated by Jupiter’s magnetic field split water molecules in the Europan atmosphere.

The STScI group also used the STIS instrument, but instead obtained imagery of Europa’s atmosphere in ultraviolet light.

“In ultraviolet light, the surface of Jupiter looks more uniform in color than in visible light, so that allowed the Sparks team to more clearly see the silhouette image of the possible plumes on Europa as the moon passed in front of the smooth Jupiter background,” she wrote in an email message.

The Roth team also used STIS during their quest for Europa’s plumes in 2012.

Sparks said that, notwithstanding a different methodology of investigation, the STScI results are similar to those found by Roth and his colleagues.

“When we calculate in a completely different way the amount of material that would be needed to create these absorption features, it’s pretty similar to what Roth and his team found,” he explained. “The estimates for the mass are similar, the estimates for the height of the plumes are similar. The latitude of two of the plume candidates we see corresponds to their earlier work.”

These images compare the 2014 transit observed by the STSI team (left) and the 2012 spectroscopy obtained by the Roth team (right). Images courtesy NASA, European Space Agency, W. Sparks (left), L. Roth (right).

The STScI and Roth teams have not seen plumes erupting from Europa at the same times. Sparks and his colleagues observed what they believe to be water plumes in January, March, and April, 2014.

Wiseman said that detection of Europa’s plumes is difficult.

“Such plumes would be faint, probably intermittent, and the ultraviolet wavelengths of light being observed are at the high frequency edge of what Hubble can detect,” she wrote in an email message.

Sparks explained that he and his team do not claim that their work proves the plumes’ existence, though he also said Monday that he does not believe that any other explanation for the findings his team made is likely.

“In a formal sense, we have a statistically significant result,” Sparks said. “The problem is that there may be something we don’t understand about the instrument or the scene. It’s more of a subjective uncertainty than a quantitative uncertainty.”

“I’m not aware of any other plausible natural explanation for the appearance of these patches of absorption,” he continued.

Two of the water plumes that were apparently observed by Sparks and his team occurred near the south pole of Europa and one was seen near the moon’s equator.

A paper detailing the findings by the STScI team will be published in the Sept. 29 edition of Astrophysical Journal.

Saturn’s moon Enceladus is the only body in the solar system known to eject water vapor to space.

Imagery obtained by the Galileo spacecraft during the late 1990s indicated that Europa has an ocean. Observation of the moon’s magnetic fields confirmed its existence.

Wiseman said during Monday’s teleconference that NASA plans to use the James Webb Space Telescope, due to be launched in 2018, to further investigate the possible water plumes of Europa.

The James Webb Space Telescope will be launched in 2018. Artist’s conception courtesy NASA.

In addition, the European Space Agency’s Jupiter Icy Moon Mission (JUICE) and NASA’s planned Europa orbiter will have future opportunities to explore the Jovian satellite.

NOTE 2: This post was updated at 9:32 pm MDT on Sept. 27, 2016 to correct an inaccurate statement contained in the headline, correct several minor errors in the quotation of Dr. Jennifer Wiseman’s email communication, and correct the acronym applicable to the Space Telescope Science Institute.

NOTE 3: This post was updated at 9:37 pm MDT on Sept. 27, 2016 to clarify the difference between the Roth team’s use of the Hubble Space Telescope’s Imaging Spectrograph in 2012 and the STScI team’s use of that instrument in 2014.

A probe launched by NASA in 2006 has resumed communication with the agency after nearly 23 months of silence.

The STEREO-B spacecraft, which orbits the sun, lost contact with Earth on Oct. 1, 2014.

The Deep Space Network reestablished the link with STEREO-B at 6:21 pm EDT on Sunday.

The long interruption in communication with the spacecraft was most likely the result of a series of events that began with a test of its command loss timer. The device is a kind of automated switch that allows the spacecraft to recover after a hardware failure. It functions by re-setting the hardware if no commands are received for a certain period of time. In STEREO-B’s case, that re-set time was three days.

NASA explained a likely scenario for the communications failure at a website posted shortly after the loss of contact event and still available here. An animated film that provides one possible model for the probe’s communication failure is also available.

STEREO-B’s navigation system probably failed because it was unable to detect guide stars. This caused the probe’s high gain antenna to be pointed away from Earth, which meant that it could not receive a signal. The breakdown in the star tracking system was likely the result of a failed laser.

“Basically, we made a mistake in not accounting for one of those individual lasers failing,” Dr. Joseph Gurman, the STEREO project scientist at NASA’s Goddard Space Flight Center, said. “The data still looked good coming out of the unit as a whole even though one laser was bad. That got us into a situation where the spacecraft was getting bad navigational information.”

STEREO-B remains in an uncontrolled spin, a problem for which there is not currently enough power available to correct. The spacecraft obtains energy by means of solar arrays that extend out from its main section.

Gurman explained that NASA scientists are not sure how much power the probe’s batteries can produce or whether they can be fully re-charged.

“We don’t know if the batteries are damaged,” he said. “We know they can take some charge.”

Whether the spacecraft’s instrumentation is still functional is also unknown.

“I would say that we know nothing about the state of the instruments at this point,” Gurman said.

NASA will proceed cautiously to investigate the STEREO-B probe’s status. What Gurman and his colleagues want to avoid is any command that would return STEREO-B to an uncontrolled spin.

“We have an inertial problem that is giving bad information to the control system on the spacecraft,” he said. “We have to proceed in a step-by-step method.”

The first step will be to figure out the extent to which the probe has, to put it metaphorically, any gas in its tank.

“We have to heat up the probably frozen fuel in the fuel tank,” Gurman explained. “We can proceed from there to use the thrusters to right our attitude by using the autonomy software.”

Gurman is optimistic, though, about the prospects for obtaining more data about the sun from STEREO-B. NASA’s prior experience with another spacecraft that experienced a communication failure – the Solar and Heliospheric Observatory – indicates that instruments can survive with little or no damage, even in the cold of space, for quite some time.

“On SOHO, there were 12 principal investigator experiments,” Gurman said. “Only one mechanism in one telescope was damaged in such a way that we really couldn’t use the instrument. There was one instrument that suffered some degradation. That’s about it. We’re cautiously optimistic that we’ll be able to regain most of the scientific capability, if not all, that we had before.”

In any case, the STEREO mission formally ended eight years ago, so any data obtained from STEREO-B is beyond what was expected at the time of launch.

“Anything we get is gravy, to say the least,” Gurman said.

The probe’s twin, STEREO-A, also revolves around our closest star.

STEREO is an acronym that shortens the twin probes’ formal name – Solar Terrestrial Relations Observatories.

A private company succeeded Friday in landing a rocket upright at sea for the first time in history.

SpaceX, which handles cargo launches for the International Space Station, said on its Twitter feed that the first stage of a Falcon 9 rocket that had lifted the Dragon cargo capsule to orbit had landed on a floating barge.

Scott Kelly arrived in Houston today aboard a small aircraft after a Russian Soyuz spacecraft brought him and several other crewmembers from the International Space Station back to the planet’s surface yesterday.

A Russian Soyuz TMA-18M spacecraft carrying NASA astronaut and space station Commander Scott Kelly, as well as Russian cosmonauts Mikhail Kornienko and Sergey Volkov, descends near the town of Zhezkazgan, Kazakhstan on Wednesday, March 2, 2016 (Kazakh time). Photo courtesy NASA, photo by Bill Ingalls.

The purpose of Kelly’s long stay in space was to examine the impacts of a low gravity environment on human health. NASA used Kelly’s Earth-bound twin brother, Mark Kelly, as a control.

During his American record-breaking stay in space, Kelly posted numerous spectacular images of Earth and space. This one is from this year’s “leap day,” Feb. 29:

The sun from the International Space Station, Feb. 29, 2016. Courtesy Scott Kelly.

Kelly saw 10,944 sunrises and sunsets during his 11-plus months aboard the ISS.

Of course, Kelly’s mission was not all about photography and videography. He also participated in efforts to grow flowers and plants aboard the ISS, an experiment aimed at assessing the viability of producing food while on the way to and from Mars.

During his time in space Kelly’s rate of aging slowed. Astrophysicist Neil DeGrasse Tyson made that point in a tweet posted Wednesday:

Welcome back to Earth, Scott Kelly. After a year in orbit, Relativity says you’re 1/100 sec younger than you’d otherwise be.

Kelly, 52, has been an astronaut for nearly 20 years and is a veteran of two space shuttle flights and several expeditions to the ISS.

A retired U.S. Navy captain, Kelly is also a highly experienced pilot. According to his official NASA biography, Kelly has flown over 8,000 hours in more than 40 different aircraft. Those included two combat aircraft: the F-14 Tomcat and the F/A-18 Hornet. He has landed an airplane on the deck of an aircraft carrier more than 250 times.

Kelly’s twin brother, Mark Kelly, is also a retired naval officer and former astronaut. Mark Kelly is the husband of former U.S. representative Gabrielle Giffords, who was the victim of an assassination attempt in 2011.

NASA’s Cassini spacecraft made its last fly-by of Enceladus on Dec. 19. Since then it has been transmitting to Earth images taken of the ocean moon, including this beauty received Feb. 15:

This view of Enceladus is from about 83,000 kilometers. The moon is captured in winter. It’s north pole is to the upper left, while its south pole is obscured by darkness in the lower right. Courtesy NASA, Jet Propulsion Laboratory, Space Science Institute, Justin Cowart.

The race to develop a rocket that can land itself after traveling to Earth orbit continued Friday as Blue Origin successfully returned a vehicle to the planet’s surface for the second time.

Blue Origin’s feat marks the first time that re-use of a rocket has been demonstrated to be feasible.

The launch of the Jeff Bezos-owned company’s New Shepard rocket occurred in west Texas. After traveling 101.7 kilometers into the atmosphere, the rocket landed vertically at spot near its launch location.

“The very same New Shepard booster that flew above the Karman line and then landed vertically at its launch site last November has now flown and landed again, demonstrating reuse,” Bezos said in a statement posted on the Blue Origin website.

Bezos was referring to an altitude generally regarded as the boundary between Earth’s atmosphere and space.

Blue Origin had previously launched and landed the same rocket in November 2015.

The company has not yet matched the altitude achievement of rival SpaceX. On Dec. 21 that firm returned a rocket that had traveled to orbit to a safe landing on Earth’s surface.

More recently SpaceX experienced a setback when an attempt to land a rocket at sea failed. One of the legs on the company’s Falcon 9 rocket collapsed when the vehicle touched down Jan. 17 on a floating barge, causing the rocket to tip over and explode.